The present invention relates generally to clinical instruments for the examination of eyes, and more particularly to a portable instrument for measurement of the interpupillary distance.
Interpupillary distance measurements are made by opticians, optometrists and ophthalmologists for clinical purposes, prescriptions for eyeglasses, and similar and related purposes. Previously available devices for measurement of interpupillary distances may be exemplified by those described by or referenced in U.S. Pat. Nos. 2,361,534 and 4,244,639. Existing devices normally require a separate operator to focus and/or align the optics thereof, to make measurements and to interpret results.
The invention provides a simple, cost effective, accurate and reliable subject operated instrument for measurement of the interpupillary distance. The invention presents recognizable optical images to respective eyes of a subject sighting along the optical axes of a pair of parallel sighting tubes. The tubes are movable with respect to each other and are interconnected by a scale for displaying the spacing between the optical axes. The subject adjusts the separation of the tubes until the images appear superimposed and reads the interpupillary distance from the scale.
It is, therefore, a principal object of the invention to provide an improved eye examinaton instrument.
It is another object of the invention to provide a subject operated instrument for measurement of the interpupillary distance.
These and other objects of the invention will become apparent as the detailed description of representative embodiments proceeds.